For ultra-high frequency operation, e.g., in the 77 GHz auto radar band and above, transistors with very high fMAX (>250 GHz) and low high frequency noise are needed. Higher frequency bands, e.g., the 94+ GHz imaging band, will require even higher performance devices. While semiconductor devices employing III-V compounds are useful in these very high frequency bands, such devices are generally more expensive than is desired. A silicon based solution is desirable for ease of integration with other complex electronic functions and for low cost manufacturing. Self-aligned emitter-base silicon-germanium hetero-junction bipolar transistors (HBTs) are potential candidates for such very high frequency devices, provided that the current device performance limitations can be overcome. For example, the extrinsic base resistance Rbx is currently larger than desired and detracts from the overall device performance. Accordingly, a need continues to exist for structures and methods of manufacture of bipolar transistors that avoid or mitigate these and other limitations of the current art.